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United States Patent |
5,693,724
|
Green
|
December 2, 1997
|
Low VOC curable coating composition utilizing carbamate-functional
compound
Abstract
There is described a curable coating composition comprising:
(A) a carbamate-functional component that is the reaction product of:
(1) a compound having a plurality of hydroxyl groups that is the reaction
product of:
(a) a compound comprising at least one epoxide group and
(b) a compound comprising a plurality of organic acid groups,
(2) a compound comprising a carbamate group, and
(B) a component comprising a plurality of groups that are reactive with the
carbamate functional groups on component (A).
Inventors:
|
Green; Marvin L. (Brighton, MI)
|
Assignee:
|
BASF Corporation (Southfield, MI)
|
Appl. No.:
|
673937 |
Filed:
|
July 1, 1996 |
Current U.S. Class: |
525/481; 525/488; 525/510; 525/514; 525/528 |
Intern'l Class: |
C08G 008/28; C08G 059/14; C08L 063/00; C08L 067/04 |
Field of Search: |
525/510,514,481,488,528
|
References Cited
U.S. Patent Documents
5356669 | Oct., 1994 | Rehfuss | 427/407.
|
Primary Examiner: Wilson; Donald R.
Attorney, Agent or Firm: Marshall; Paul L., Budde; Anne M.
Claims
What is claimed is:
1. A curable coating composition comprising:
(A) a carbamate-functional component that is the reaction product of:
(1) a compound having a plurality of hydroxyl groups that is the ungelled
reaction product of:
(a) a compound comprising at least one epoxide group and
(b) a compound comprising a plurality of organic acid groups selected from
the group consisting of carboxylic acid groups, phenolic groups, and
mixtures thereof;
(2) a compound comprising a carbamate group, and
(B) a component comprising a plurality of groups that are reactive with the
carbamate functional groups on component (A).
2. A curable coating composition according to claim 1 wherein said compound
(A)(1)(a) is a glycidyl ether.
3. A curable coating composition according to claim 1 wherein said compound
(A)(1)(a) is a glycidyl ester.
4. A curable coating composition according to claim 3 wherein said glycidyl
ester has the formula:
##STR5##
wherein R is a hydrocarbon group of from 1 to 40 carbon atoms.
5. A curable coating composition according to claim 4 wherein R is a
hydrocarbon group of from 1 to 12 carbon atoms.
6. A curable coating composition according to claim 1 wherein said compound
(A)(1)(a) comprises a plurality of epoxide groups.
7. A curable coating composition according to claim 1 wherein said compound
(A)(1)(a) comprises a single epoxide group.
8. A curable coating composition according to claim 1 wherein said compound
(A)(1)(a) is the glycidyl ester of neodecanoic acid.
9. A curable coating composition according to claim 1 wherein said organic
acid groups are carboxylic acid groups.
10. A curable coating composition according to claim 1 wherein component
(B) is an aminoplast resin.
11. A Curable coating composition according to claim 11 wherein said
aminoplast resin is a melamine resin.
12. A curable coating composition according to claim 1 having a VOC of less
than 3.8 lbs/gal.
13. A curable coating composition according to claim 12 having a VOC of
less than 3.0 lbs/gal.
14. A curable coating composition according to claim 13 having a VOC of
less than 2.0 lbs/gal.
15. A curable coating composition according to claim 14 having a VOC of
less than 1.0 lbs/gal.
16. A cured coating comprising the reaction product of a coating
composition according to claim 1.
17. A cured coating according to claim 16 having a crosslink density of at
least 3.
18. A cured coating according to claim 17 having a crosslink density of at
least 10.
19. A coating according to claim 18 having a 20.degree. gloss, as defined
by ASTM D523-89, of at least 80.
20. A coating according to claim 16 having a DOI, as defined by ASTM
E430-91, of at least 80.
Description
FIELD OF THE INVENTION
This invention relates to curable coating compositions, particularly to
curable compositions utilizing a carbamate-functional compound as one of
the components of the composition.
BACKGROUND OF THE INVENTION
Curable coating compositions such as thermoset coatings are widely used in
the coatings art. They are often used for topcoats in the automotive and
industrial coatings industry. Color-plus-clear composite coatings are
particularly useful as topcoats where exceptional gloss, depth of color,
distinctness of image, or special metallic effects are desired. The
automotive industry has made extensive use of these coatings for
automotive body panels. Color-plus-clear composite coatings, however,
require an extremely high degree of clarity in the clearcoat to achieve
the desired visual effect. High-gloss coatings also require a low degree
of visual aberations at the surface of the coating in order to achieve the
desired visual effect such as high distinctness of image (DOI).
Such coatings are especially susceptible to a phenomenon known as
environmental etch. Environmental etch manifests itself as spots or marks
on or in the finish of the coating that often cannot be easily rubbed out.
It is also often desirable to provide options of different types of
carbamate-functional materials to provide coatings with a good combination
of properties such as durability, hardness, flexibility, and resistance to
scratching, marring, solvents, and acids.
Curable coating compositions based on curable components having carbamate
functionality have been described in the art to provide etch-resistant
coatings, e.g., U.S. Pat. No. 5,356,669 and WO 94/10211. Non-polymeric
carbamate-functional compounds for coating compositions have been
described in U.S. Pat. No. 5,336,566 and EP 636,660.
In order to obtain the smooth finishes that are often highly desirable in
the coatings industry, coating compositions preferably tend to be fluid in
nature, and to exhibit good flow. Good flow is observed when the coating
composition is fluid enough at some point after it is applied to the
substrate and before it cures to a hard film so that the surface of the
coating takes on a smooth appearance. Some coating compositions exhibit
good flow immediately upon application and others exhibit good flow when
heated. One way to impart fluid characteristics and good flow to a coating
composition is to incorporate volatile organic solvents into the
compositions. These solvents can provide the desired fluidity and flow
during the coating process, after which they evaporate, leaving only the
coating components behind. However, the use of such solvents also
increases the volatile organic content (VOC) of the coating composition.
Because of the adverse impact VOC has on the environment, many government
regulations impose limitations on the amount of solvent that can be used.
It would thus be desirable to utilize coating composition components that
provide good fluidity and flow to the coating composition without the need
for large amounts of solvent.
Because of their other beneficial properties, it would also be desirable to
provide carbamate-functional compounds for use in coating compositions
that do not require large quantities of solvent.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a curable coating
composition comprising:
(A) a carbamate-functional component that is the reaction product of:
(1) a compound having a plurality of hydroxyl groups that is the reaction
product of:
(a) a compound comprising at least one epoxide group and
(b) a compound comprising a plurality of organic acid groups,
(2) a compound comprising a carbamate group, and
(B) a component comprising a plurality of groups that are reactive with the
carbamate functional groups on component (A).
Compositions of the present invention can reduce the need for organic
solvents, and can also impart to coating compositions the ability to spray
apply at high viscosities while still maintaining good flow and appearance
characteristics.
The present invention provides coatings having a good combination of
properties such as durability, hardness, and resistance to scratching,
marring, solvents, and acids. Coating compositions according to the
invention can also provide low VOC levels while maintaining other
beneficial properties that are often found in coating compositions
containing relatively high amounts of solvent, such as good sag
resistance, leveling, low orange peel, gloss, DOI, wetting of the
substrate, and pigment dispersing and loading, and uniform cure.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
According to the invention, compound (A)(1) comprises a plurality of
hydroxyl groups and is the reaction product of (a) a compound comprising
at least one epoxide group and (b) a compound comprising a plurality of
organic acid groups. The reaction between the epoxide compounds (a) and
(b) is believed to be a ring-opening reaction between the epoxy group and
the organic acid group. This reaction often utilizes carboxylic acid
groups, although other organic acids such as phenolic compounds may be
used as well. The acid/epoxy reaction is well-known in the chemical arts,
and may proceed spontaneously at ambient conditions, either in solvent or
neat, and may be advantageously accelerated with heat.
Compound (A)(1) may be a monoepoxide or a polyepoxide. Virtually any
epoxide may be used in the practice of the present invention. Epoxides are
well-known in the art, and may be characterized by the general formula:
##STR1##
where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are each independently H (with
the proviso that at least one of R.sup.1 -R.sup.4 is other than H), an
organic radical, which may be polymeric or non-polymeric and may contain
unsaturation and/or heteroatoms, or one of R.sup.1 or R.sup.2 together
with one of R.sup.3 or R.sup.4 may form a cyclic ring, which may contain
unsaturation and/or heteroatoms.
Useful epoxides can be prepared from alcohols, e.g., butanol, trimethylol
propane, by reaction with an epihalohydrin (e.g., epichlorohydrin), or by
reaction of an allyl group with peroxide. The epoxide may be
monofunctional or polyfunctional, which can be controlled by selection of
the starting material. For example, a monoepoxide can be prepared by
reacting a mono-alcohol or mono-acid with an epihalohydrin or a
monounsaturate with peroxide, and a polyepoxide can be prepared by
reacting a polyol (including diols, triols, and higher-functionality
polyols) with an epihalohydrin or a polyunsaturate compound with peroxide.
Oligomeric or polymeric polyepoxides, such as acrylic polymers or
oligomers containing glycidyl methacrylate or epoxy-terminated
polyglycidyl ethers such as the diglycidyl ether of bisphenol A (DGEBPA),
can also be used. Epoxidized polyurethane resins or polyester resins can
be prepared by reacting OH group-containing polyurethanes or polyesters,
as are known in the art, with an epihalohydrin. Epoxides can also be
prepared by reacting an isocyanate-terminated component such as a
monomeric polyisocyanate (including isocyanurates, e.g., the isocyanurate
of isophorone diisocyanate) or polymer or oligomer with glycidol. Other
known polyepoxides, e.g., epoxy-novolacs, may also be used.
In one preferred embodiment, the epoxide is a monoepoxide, preferably an
epoxy ester, also known as a glycidyl ester. Glycidyl esters can be
prepared by reacting a monofunctional carboxylic acid (e.g., octanoic
acid, benzoic acid, benzylic acid, cyclohexane carboxylic acid) with an
epihalohydrin (e.g., epichlorohydrin) under conditions well-known in the
art. Glycidyl esters are commercially available, e.g., as Cardura.RTM. E
from Shell Oil Company, Glydexx.RTM. N-10 from Exxon, or Araldite.RTM.
PT910 from Ciba-Geigy. Glycidyl esters may be described by the formula:
##STR2##
wherein R is a hydrocarbon group of from 1 to 40 carbon atoms, preferably
1-20 carbon atoms, and most preferably 1-12 carbon atoms. This hydrocarbon
group may be substituted, as is known in the art. Polyglycidyl esters may
also be used, and can be prepared by reacting a polyfunctional carboxylic
acid (e.g., phthalic acid, thioglycolic acid, adipic acid) with an
epihalohydrin. Polyglycidyl esters can also be described by the above
formula where R is substituted with other glycidyl ester groups.
Another useful class of monoepoxides are glycidyl ethers. Glycidyl ethers
can be prepared by the reaction of monofunctional alcohols (e.g.,
n-butanol, propanol, 2-ethyl hexanol, dodecanol, phenol, cresol,
cyclohexanol, benzyl alcohol) with an epihalohydrin (e.g.,
epichlorohydrin). Useful glycidyl ethers include the glycidyl ether of
2-ethylhexanol, the glycidyl ether of dodecanol, the glycidyl ether of
phenol, and the like. These compounds are commercially available under the
Erisys.RTM. product family from CVC Specialties. Polyglycidyl ethers may
also be used, and can be prepared by reacting a polyfunctional alcohol
(e.g., bisphenol A, 1,6-hexane diol) with an epihalohydrin.
Epoxides may also be prepared by reacting a compound containing one or more
double bonds with peroxide or peracetic acid under conditions well-known
in the art. Virtually any double bond-containing compound may be used. One
useful class of double bond-containing compounds are cycloaliphatic
monounsaturated compounds such as
##STR3##
which may be sold as the Cyracure.RTM. products from Union Carbide. Other
double bond-containing compounds that may be used in the practice of the
invention include ethylene, propylene, styrene, styrene oxide,
cyclohexene, polybutadiene, and the like.
The epoxide may also be an acrylic-containing polymer or oligomer,
preferably deriving its epoxy groups from glycidyl methacrylate monomer,
glycidyl acrylate, allyl glycidyl ether, cyclohexyl monoepoxyy
methacrylate, the epoxide of the dimer of cylopentadiene methacrylate, or
epoxidized butadiene, more preferably glycidyl methacrylate.
The above-described epoxides are reacted with a compound (b) comprising a
plurality of organic acid groups. The use of a polyacid provides a
plurality of hydroxyl groups available for transesterification with the
carbamate compound (A)(2) even if a monoepoxide is used. Useful polyacids
include tricarballylic acid, adipic acid, azeleic acid, trimellitic
anhydride, citric acid, malic acid, tartaric acid, bisphenol F, and
bisphenol A. If the polyacid is reacted with a polyepoxide, the starting
materials and reaction conditions should be controlled so as to avoid any
unwanted chain extension or branching, which could result in high
molecular weight compounds that could increase VOC or cause gelation. If
hydroxyl groups are present on the the polyacid (e.g., citric acid), the
reaction is preferably conducted without catalyst so that unwanted
reaction of the hydroxyl groups with the epoxy groups is minimized.
The compound (A)(1) is reacted with a compound (A)(2) to form the
carbamate-functional compound (A). In one embodiment, (A)(2) is cyanic
acid, which may be formed by the well-known reaction of the thermal
decomposition of urea or by other methods, such as described in U.S. Pat.
Nos. 4,389,386 or 4,364,913. In another embodiment, (A)(2) is a compound
comprising a carbamate group. In this embodiment, the reaction between
(A)(1) and (A)(2) is believed to be a transesterification between the OH
groups on (A)(1) and the carbamate ester on compound (A)(2). The carbamate
compound (A)(2) can be any compound having a carbamate group capable of
undergoing a transesterification with the hydroxyl groups on component
(A)(1). These include, for example, methyl carbamate, butyl carbamate,
propyl carbamate, 2-ethylhexyl carbamate, cyclohexyl carbamate, phenyl
carbamate, hydroxypropyl carbamate, hydroxyethyl carbamate, and the like.
Useful carbamate compounds can be characterized by the formula:
R'--O--(C.dbd.O)--NHR"
wherein R' is substituted or unsubstituted alkyl (preferably of 1-8 carbon
atoms) and R" is H, substituted or unsubstituted alkyl (preferably of 1-8
carbon atoms, substituted or unsubstituted cycloalkyl (preferably of 6-10
carbon atoms), or substituted or unsubstituted aryl (preferably of 6-10
carbon atoms). Preferably, R" is H.
The transesterification reaction between compounds (A)(1) and (A)(2) can be
conducted under typical transesterification conditions, e.g., temperatures
from room temperature to 150.degree. C. with transesterification catalysts
such as calcium octoate, metal hydroxides (e.g., KOH), Group I or II
metals (e.g., Na, Li), metal carbonates (e.g., K.sub.2 CO.sub.3) which may
be enhanced by use in combination with crown ethers, metal oxides (e.g.,
dibutyltin oxide), metal alkoxides (e.g., NaOCH.sub.3, Al(OC.sub.3
H.sub.7).sub.3), metal esters (e.g., stannous octoate, calcium octoate, or
protic acids (e.g., H.sub.2 SO.sub.4), MgCO.sub.3, or Ph.sub.4 SbI. The
reaction may also be conducted at room temperature with a
polymer-supported catalyst such as Amberlyst-15.RTM. (Rohm & Haas) as
described by R. Anand, Synthetic Communications, 24(19), 2743-47 (1994),
the disclosure of which is incorporated herein by reference.
The ring-opening of the oxirane ring of an epoxide compound by a carboxylic
acid results in a hydroxy ester structure. Subsequent transesterification
of the hydroxyl group on this structure by the carbamate compound (A)(2)
results in a carbamate-functional component that can be represented by
either of the structures:
##STR4##
or a combination thereof, wherein n is a positive integer of at least 1,
R.sub.1 represents H, alkyl, or cycloalkyl, and R.sub.2 represents alkyl,
aryl, or cycloalkyl, and X represents an organic radical that is a residue
of the epoxide compound. As used herein, it should be understood that
these alkyl, aryl, or cycloalkyl groups may be substituted. For example,
where a monoepoxide is reacted with a polyacid, R.sub.2 in the above
structures would represent the residue of the polyacid, and would be
substituted with other carbamate group(s) resulting from the other acid
groups on the polyacid reacting with the monoepoxide followed by
transesterification with the carbamate compound (A)(2).
The composition of the invention is cured by a reaction of the
carbamate-functional compound (A) with a component (B) that is a compound
having a plurality of functional groups that are reactive with the
carbamate groups on component (A). Such reactive groups include active
methylol or methylalkoxy groups on aminoplast crosslinking agents or on
other compounds such as phenol/formaldehyde adducts, siloxane or silane
groups, and anhydride groups. Examples of (B) compounds include melamine
formaldehyde resin (including monomeric or polymeric melamine resin and
partially or fully alkylated melamine resin), urea resins (e.g., methylol
ureas such as urea formaldehyde resin, alkoxy ureas such as butylated urea
formaldehyde resin), N-methylol acrylamide emulsions, isobutoxy methyl
acrylamide emulsions, polyanhydrides (e.g., polysuccinic anhydride), and
siloxanes or silanes (e.g., dimethyldimethoxy silane). Aminoplast resin
such as melamine formaldehyde resin or urea formaldehyde resin are
especially preferred. Also useful are aminoplast resins where one or more
of the amino nitrogens is substituted with a carbamate group for use in a
process with a curing temperature below 150.degree. C., as described in
U.S. Pat. No. 5,300,328.
A solvent may optionally be utilized in the coating composition used in the
practice of the present invention. The coating composition according to
the present invention can be applied without solvent, especially if the
degree of chain extension for component (A) is limited. However, in many
cases, it is desirable to use a solvent in the coating composition as
well. This solvent should act as a solvent with respect to both the
carbamate-functional compound (A) as well as the component (B). In
general, depending on the solubility characteristics of components (A) and
(B), the solvent can be any organic solvent and/or water. In one preferred
embodiment, the solvent is a polar organic solvent. More preferably, the
solvent is a polar aliphatic solvents or polar aromatic solvents. Still
more preferably, the solvent is a ketone, ester, acetate, aprotic amide,
aprotic sulfoxide, or aprotic amine. Examples of useful solvents include
methyl ethyl ketone, methyl isobutyl ketone, amyl acetate, ethylene glycol
butyl ether-acetate, propylene glycol monomethyl ether acetate, xylene,
N-methylpyrrolidone, or blends of aromatic hydrocarbons. another
embodiment, the solvent can be water or a mixture of water with
co-solvents.
The coating composition used in the practice of the invention may include a
catalyst to enhance the cure reaction. For example, when aminoplast
compounds, especially monomeric melamines, are used as component (B), a
strong acid catalyst may be utilized to enhance the cure reaction. Such
catalysts are well-known in the art and include, for example,
p-toluenesulfonic acid, dinonylnaphthalene disulfonic acid,
dodecylbenzenesulfonic acid, phenyl acid phosphate, monobutyl maleate,
butyl phosphate, and hydroxy phosphate ester. Other catalysts that may be
useful in the composition of the invention include Lewis acids, zinc
salts, and tin salts.
Although a solvent may be present in the coating composition in an amount
of from about 0.01 weight percent to about 99 weight percent, it is
preferably present in an amount of less than 30%, more preferably less
than 20% and most preferably less than 10%. The coating composition
preferably has a VOC (VOC is defined herein as VOC according to ASTM
D3960) of less than 3.8 lbs/gal, more preferably less than 3.0 lbs/gal,
even more preferably less than 2.0 lbs/gal, and most preferably less than
1.0 lbs/gal.
Coating compositions can be coated on the article by any of a number of
techniques well-known in the art. These include, for example, spray
coating, dip coating, roll coating, curtain coating, and the like. For
automotive body panels, spray coating is preferred. One advantage that can
be achieved with coating compositions according to the invention is that
coatings with a high degree of flexibility can be prepared. Accordingly,
in a preferred embodiment, the substrate onto which the coating is applied
is flexible, such as plastic, leather, or textile substrates.
Any additional agent used, for example, surfactants, fillers, stabilizers,
wetting agents, dispersing agents, adhesion promoters, UV absorbers, HALS,
etc. may be incorporated into the coating composition. While the agents
are well-known in the prior art, the amount used must be controlled to
avoid adversely affecting the coating characteristics.
In one preferred embodiment, the coating composition according to the
invention is preferably utilized in a high-gloss coating and/or as the
clearcoat of a composite color-plus-clear coating. High-gloss coatings as
used herein are coatings having a 20.degree. gloss (ASTM D523-89) or a DOI
(ASTM E430-91) of at least 80. In other preferred embodiments, the coating
composition may be utilized to prepare high-gloss or low-gloss primer or
enamel coatings.
When the coating composition of the invention is used as a high-gloss
pigmented paint coating, the pigment may be any organic or inorganic
compounds or colored materials, fillers, metallic or other inorganic flake
materials such as mica or aluminum flake, and other materials of kind that
the art normally names as pigments. Pigments are usually used in the
composition in an amount of 2% to 350%, based on the total weight (not
including solvent) of components A and B (i.e., a P:B ratio of 0.02 to
3.5).
When the coating composition according to the invention is used as the
clearcoat of a composite color-plus-clear coating, the pigmented basecoat
composition may any of a number of types well-known in the art, and does
not require explanation in detail herein. Polymers known in the art to be
useful in basecoat compositions include acrylics, vinyls, polyurethanes,
polycarbonates, polyesters, alkyds, and siloxanes. Preferred polymers
include acrylics and polyurethanes. In one preferred embodiment of the
invention, the basecoat composition also utilizes a carbamate-functional
acrylic polymer. Basecoat polymers are preferably crosslinkable, and thus
comprise one or more type of cross-linkable functional groups. Such groups
include, for example, hydroxy, isocyanate, amine, epoxy, acrylate, vinyl,
silane, and acetoacetate groups. These groups may be masked or blocked in
such a way so that they are unblocked and available for the cross-linking
reaction under the desired curing conditions, generally elevated
temperatures. Useful cross-linkable functional groups include hydroxy,
epoxy, acid, anhydride, silane, and acetoacetate groups. Preferred
cross-linkable functional groups include hydroxy functional groups and
amino functional groups.
Basecoat polymers may be self-cross-linkable, or may require a separate
cross-linking agent that is reactive with the functional groups of the
polymer. When the polymer comprises hydroxy functional groups, for
example, the cross-linking agent may be an aminoplast resin, isocyanate
and blocked isocyanates (including isocyanurates), and acid or anhydride
functional cross-linking agents.
The coating compositions described herein are preferably subjected to
conditions so as to cure the coating layers. Although various methods of
curing may be used, heat-curing is preferred. Generally, heat curing is
effected by exposing the coated article to elevated temperatures provided
primarily by radiative heat sources. Curing temperatures will vary
depending on the particular blocking groups used in the cross-linking
agents, however they generally range between 93.degree. C. and 177.degree.
C. The coating composition according to the present invention is curable
even at relatively low cure temperatures. Thus, in a preferred embodiment,
the cure temperature is preferably between 115.degree. C. and 150.degree.
C., and more preferably at temperatures between 115.degree. C. and
138.degree. C. for a blocked acid catalyzed system. For an unblocked acid
catalyzed system, the cure temperature is preferably between 82.degree. C.
and 99.degree. C. The curing time will vary depending on the particular
components used, and physical parameters such as the thickness of the
layers, however, typical curing times range from 15 to 60 minutes, and
preferably 15-25 minutes for blocked acid catalyzed systems and 10-20
minutes for unblocked acid catalyzed systems.
In a number of embodiments of the present invention, the curable coating
composition, when cured, can result in coatings having a surprising
combination of high cross-link density without becoming brittle. As used
herein, crosslink density is determined as described in the "Paint and
Coatings Testing Manual", Gardner-Sward Handbook, 14th ed., chapt. 46, p.
534, ASTM, 1995. Crosslink density is expressed in moles/cm.sup.3 and is
calculated using the formula
##EQU1##
where .upsilon..sub.e =moles of elastically effective network chains per
cubic centimeter of film, the storage modulus values, G' or E', are
obtained in the rubbery plateau, T is temperature in degrees K
corresponding to the storage modulus value, and R is the gas constant
(8.314.times.10.sup.7 dynes/deg. K.multidot.mole). Thus, one embodiment of
the invention is directed toward a cured coating derived from the
above-described curable coating compositions, which has a cross-link
density of at least 3, and preferably at least 10.
The invention is further described in the following examples.
Preparation 1
In the first step, 120 parts of dimethylolpropionic acid (DMPA), a 25%
aliquot of the stoichiometric ratio, was charged with 943 parts of
Glydexx.RTM. N-10 glycidyl neodecanoate to a reaction vessel. The mixture
was heated to a temperature of 128.degree. C. After a slight exotherm,
three more 25% increments of 120 parts of the DMPA were added spaced over
a 4-hour period and the temperature was maintained at 130.degree. C. The
reaction was monitored via acid number to a value of <3 and contained no
residual epoxy groups.
In step two, 1211 parts of methyl carbamate, a 50% excess, was added along
with 10 parts of dibutyltin oxide catalyst and 950 parts of toluene. A
reflux temperature of 109.degree.-117.degree. C. was maintained for 32
hours as methanol was trapped off. The progress of the reaction was
monitored by hydroxyl number to at least 95% completion. The excess methyl
carbamate and solvent were stripped off and 450 parts of amyl acetate was
added to reduce to a non-volatile content of 80%.
Preparation 2
In the first step, 89 parts of citric acid, a 25% aliquot of the
stoichiometric ratio, was charged with 1470 parts of Glydexx.RTM. N-10
glycidyl neodecanoate to a reaction vessel. The mixture was heated to a
temperature of 128.degree. C. After a slight exotherm, three more 25%
increments of 89 parts of the citric acid were added spaced over a 4-hour
period and the temperature was maintained at 130.degree. C. The reaction
was monitored via acid number to a value of <3 and contained no residual
epoxy groups.
In step two, 840 parts of methyl carbamate, a 50% excess, was added along
with 12.8 parts of dibutyltin oxide catalyst and 1200 parts of toluene. A
reflux temperature of 109.degree.-117.degree. C. was maintained for 32
hours as methanol was trapped off. The progress of the reaction was
monitored by hydroxyl number to at least 95% completion. The excess methyl
carbamate and solvent were stripped off and 425 parts of amyl acetate was
added to reduce to a non-volatile content of 80%.
EXAMPLE 1
A coating composition was prepared by mixing 84 parts of the product of
Preparation 1 with 27 parts of a commercial liquid hexamethoxymethyl
melamine resin. Also, 4 parts of blocked dodecylbenzene sulfonic acid
catalyst along with 22 parts of amyl acetate were added to give a coating
composition with 61% weight non-volatile content. The coating composition
was sprayed onto a panel over a conventional high-solids basecoat
containing a hydroxy-functional acrylic polymer and a melamine resin
curing agent, and cured for 20 minutes at 132.degree. C. metal
temperature. The resulting coating exhibited good film properties as
measured by humidity resistance, solvent resistance, hardness, etch
resistance, gravelometer, and weathering resistance.
EXAMPLE 2
A coating composition was prepared by mixing 97 parts of the product of
Preparation 2 with 19 parts of a commercial liquid hexamethoxymethyl
melamine resin. Also, 4 parts of blocked dodecylbenzene sulfonic acid
catalyst along with 20 parts of amyl acetate were added to give a coating
composition with 64% weight non-volatile content. The coating composition
was sprayed onto a panel over a conventional high-solids basecoat
containing a hydroxy-functional acrylic polymer and a melamine resin
curing agent, and cured for 20 minutes at 132.degree. C. metal
temperature. The resulting coating exhibited good film properties as
measured by humidity resistance, solvent resistance, hardness, etch
resistance, gravelometer, and weathering resistance.
The invention has been described in detail with reference to preferred
embodiments thereof. It should be understood, however, that variations and
modifications can be made within the spirit and scope of the invention.
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